Sulphur cycle is a biogeochemical cycle by which sulphur moves to and from minerals and living systems. Which of the following bacteria reduces sulphate ions to hydrogen sulphide in the process of sulphur cycle?

The direct reduction of sulphate ions to hydrogen sulphide is effected in nature by specialised, strictly anaerobic bacterium of the genus Desulfotomaculum. These sulphate reducing bacteria (SRB) are heterotrophic organisms that utilise sulphate, thiosulphate, S2O3--, sulphite, SO3-- or other reducible sulphur-containing ions as terminal electron acceptors in their respiratory metabolism. In the process, these sulphur-containing ions are reduced to hydrogen sulphide.